Abstract: A system used to synchronize the clock frequency of a receiver with that of a transmitter, where both the receiver and transmitter communicate using the ADSL Annex C standard. The transmitter continuously transmits pilot tones to the receiver. The receiver determines the phase error between sequential pilot tone symbols to determine a phase error. The receiver uses the phase error to adjust the receiver clock frequency. However, if the most recently received symbol is subject to near end crosstalk or is subject to far end crosstalk and is a boundary symbol, the receiver ignores the phase error and does not adjust the receiver clock frequency.

Abstract: A system used to synchronize the clock frequency of a receiver with that of a transmitter, where both the receiver and transmitter communicate using the ADSL Annex C standard. The transmitter continuously transmits pilot tones to the receiver. The receiver determines the phase error between sequential pilot tone symbols to determine a phase error. The receiver uses the phase error to adjust the receiver clock frequency. However, if the most recently received symbol is subject to near end crosstalk or is subject to far end crosstalk and is a boundary symbol, the receiver ignores the phase error and does not adjust the receiver clock frequency.

Abstract: A system used to synchronize the clock frequency of a receiver with that of a transmitter, where both the receiver and transmitter communicate using the ADSL Annex C standard. The transmitter continuously transmits pilot tones to the receiver. The receiver determines the phase error between sequential pilot tone symbols to determine a phase error. The receiver uses the phase error to adjust the receiver clock frequency. However, if the most recently received symbol is subject to near end cross talk or is subject to far end cross talk and is a boundary symbol, the receiver ignores the phase error and does not adjust the receiver clock frequency.

Abstract: A system for attenuating noise which can be sensed by the auditory nerve comprising a microphone positioned in a first sound region for sensing noise present in the first sound region for creating a first electrical signal having a frequency and amplitude corresponding to the noise sensed in the first sound region. Circuitry is provided for processing the first electrical signal to create a second electrical signal having the same frequency but of opposite amplitude and sign of the first electrical signal. A speaker is provided for converting the second electrical signal to anti-noise for attenuation of the sensed noise in a second sound region spaced from the first sound region. A microphone is disposed in the second sound region for detecting any noise above a predetermined noise level in the second sound region to provide an error correction signal.

Abstract: Sleep apnea screening and/or detection apparatus for use by a patient breathing through the nose and/or mouth and producing an air flow into and out of the lungs of the patient and creating audible sounds. It is comprised of a first microphone positioned in the vicinity of the patient's nose and mouth and out of contact therewith to pick up audible sounds created by breathing of the patient and providing a first electrical analog signal. A second microphone is provided which is positioned near the patient for picking up ambient noise in the vicinity of the patient and providing a second electrical analog signal, an active noise controller is provided for combining the first and second electrical analog signals to provide a third electrical signal for generating a fourth electrical signal providing a waveform which is closely correlated with the air flow of the patient.